This invention relates to a high-density tissue culture system utilizing zero gravity to facilitate the cultivation of eucaryotic cells that require attachment to substratum to differentiate and to produce desired products of biomedical interests.
Many biological products such as hormone releasing factors from hypothalamus are difficult to isolate in large quantities by conventional biochemical extraction procedures since their presence is in minute quantities. With current advancement of recombinant DNA studies, it is possible to produce large quantities of "pure" products if their molecular sizes are not larger than insulin molecules. For larger molecules, isolations and insertions of the genes are exceedingly difficult because there may be more cistrons required than just the structural genes themselves. Thus, utilization of eucaryotic cell lines or primary cultures that synthesize specialized products is more practical.
For most normal differentiated cells, a substratum and attachment are required for them to proliferate, to differentiate, and to synthesize specialized products. A large surface area is required to obtain large cell members.
One system which has been particularly successful in large scale culture of cells requiring substratum attachment utilizes roller bottles. The interior of the roller bottle provides the necessary growing surface, and rotation of the bottle provides a continuous exchange of nutrient and gas between the medium therein and the eucaryotic cells. However, to obtain cell culture on a large scale, a lot of bottles are needed which requires a large room for the roller racks.
Suspension culture has been relatively successful in application to cells which do not require stratum attachment to proliferate and differentiate. However, as the cell density increases, the cells adhere to each other and settle to the bottom of the culture vessel. There, either the cells undergo contact inhibition of growth, the gaseous exchange between the underlayers of cells and the medium is impaired, or the toxic metabolic waste accumulates and harms the cells. Further, a spinner is necessary to suspend and maintain suspension of the cells but the spinner generates shearing forces which are injurious to the suspended cells.